Calorie Restriction and Longevity
Calorie restriction (usually abbreviated to CR) is a strategy proven to extend healthy and maximum life span in rodents and primates. Some animal studies conducted over the past 20 years have shown up to a 40% increase in maximum life span.
Calorie restriction also provides numerous secondary benefits, such as a greatly lowered risk for most degenerative conditions of aging, and improved measures of general health. In recent years, human studies have demonstrated that these same secondary health benefits are available to you and I, not just to laboratory animals. Many researchers believe that the evidence to date shows the practice of CR will extend the healthy human life span, but a consensus has not yet been reached on this topic.
Clive M. McCay, a nutritional scientist at Cornell University in New York, was one of the first and most successful scientific investigators in the antiaging field. He sought to determine if calorie restriction would extend the life span by posing himself a question: if we slow the growth and development of an animal, do we also slow its decline? McCay conducted the first widely recognized scientific study to demonstrate that a calorie-restricted diet (but not a diet reduced in nutrients) did enable animals to live longer. He fed a group of rats a diet containing 20 percent indigestible cellulose, which reduced’ their caloric intake by approximately 40 percent, and found that it extended their life span by as much as 40 percent to 50 percent. Not only did the diet dramatically slow the rate of aging, but it also delayed the onset of diseases related to aging such as cancer, heart disease, and brain disease.
McCay’s longest-lived calorie-restricted rats survived for fortyeight months, while his “control” (by induding the control, or placebo, arm of the study, more reliable data are obtained) animals, who were fed a normal diet, died at the expected age of thirty months. Later experiments by other researchers kept rats alive for more than fiftynine months-almost twice the normal life span. Since the 1930s, scientists around the world have confirmed the powerful effects of calorie restriction on animals. The same result has been observed in almost every laboratory animal tested. Yeast, worms, flies, mice, rats, and fish-all have responded to calorie restriction by living longer, with a lower incidence of most age-associated diseases. This approach has consistently proven to be the most effective way of extending the maximum life span of animals. It has also been discovered that the effects of calorie restriction are dose dependent-that is, the greater the degree of calorie restriction, the greater its effects, provided that the animal consumes balanced nutrients and eats enough to avoid starvation.
As one might imagine, this information has sparked the efforts of scientist hoping to replicate the animal test results in humans. The major problem is that a person needs to overcome a lifetime of eating habits (as well as hunger pangs) to obtain these potential benefits. The Calorie Restriction Society, a nonprofit organization that advocates this diet and lifestyle, estimates that a person needs to maintain a body weight of approximately 25 percent less than the medically established ideal weight. In terms of calorie consumption, this means approximately 40 percent less per day than the normal recommended diet. For women, dietitians and nutritionists usually recommend around 2,000 calories per day, and for men, 2,500 calories. This is quite variable, depending on body mass and activity level.
How to fight aging with calorie restriction diet plan?
Pay Attention to Calories
Counting calories is a good thing, and it’s something that you have to pay attention to. Your body will let you eat far more than is good for you, so your brain is going to have to take over managing the process.
Remember the Supplements
You should always take a good multivitamin supplement (at the very least) when on a calorie restriction diet. In theory, it’s perfectly possible to obtain all the vitamins and micronutrients you need from your food. In practice, for most people living busy, working lives, this just isn’t going to happen. Remember to take your supplements.
Drink lots of water
Doctors tell us that few people in Western societies drink as much water as they should for optimal health, and many people mistake low-level thirst for low-level hunger. A very helpful tactic for those practicing calorie restriction is to drink a glass of water when first feeling hungry. If you are still hungry twenty minutes later, then maybe it’s time to think about eating. Half the time, you were just thirsty, however.
The risks and discomforts of such a diet, especially if it is not balanced, are many-including unattractive appearance changes, diminished bone mass, cold sensitivity, reduced energy reserves, and constant hunger. Severe calorie restriction also can cause menstrual irregularity and interfere with reproductive function in women, as well as reduce muscle mass, decrease testosterone in men, and slow wound healing. If one chooses to participate in such a diet, it must be nutritionally balanced in terms of carbohydrates, fats, and proteins. Needless to say, if you opt for such a restricted diet, you may live longer, but your quality of life may also be greatly diminished.
Nearly two hundred years before McCay conducted his experiments, Benjamin Franklin observed, “To lengthen thy life, lessen thy meals.” With two-thirds of the American population currently either overweight or obese, his words ring powerfully today. So what does the evidence show in people?
Because of the suffering associated with severe calorie restriction, it has been difficult to design human experiments in this area. Still, several studies have been conducted that are worth noting. Physiologist Ancel Keys carried out one of the earliest at the University of Minnesota in the 1950s. He compared sixty volunteers who ate an average dai1y diet of 1,500 calories for three years with a control group who consumed 2,300 calories per day. Although the study was inconclusive as concerns longevity, it did demonstrate that the calorie restricted group was healthier. (Keys, incidentally, lived to be one hundred.) Its members made fewer visits to the infirmary. for example, and blood tests also showed them to be healthier than the control group.
Another well-documented study of calorie restriction evaluated dietary habits in a part of Japan known for its inhabitants’ longevity. Researchers found that both children and adults in Okinawa consumed between 20 percent and 30 percent fewer calories than the national average. Okinawan death rates from stroke, cancer, and heart disease were lower by approximately 60 percent, and the number of centenarians on the island was forty times greater than that of the northeast part of Japan, where calorie intake was normal. Again, these results are consistent with animal studies showing that calorie restriction increases the life span and reduces the incidence and severity of agerelated diseases.
In August 2007 three studies seemed to confirm that calorie restriction in humans, as in animals, adds to longevity. The first appeared in the American Journal of Cardiology. Scientists looked at the heart function of twenty-five people who had been calorie restricted for about six years. They ate 1,400 to 2,000 nutritionally balanced calories per day and were compared with a matched control group that ate a typical 2,000 to 3,000 calories daily. Using ultrasonic imaging to evaluate heart function, scientists found that the calorie-restricted hearts were more elastic and resembled hearts fifteen years younger than their actual age.
The Genes behind Calorie Restriction
Despite the dramatic study results by McCay in the 1930s, just how calorie restriction worked to increase longevity was still unknown. Over the next five decades, many theories evolved. Dr. Denham Harman, a professor at the University of Nebraska, speculated that dietary restriction reduced energy production in the cells and therefore led to less toxicity from freeradicals. That made intuitive sense. Theoretically, fewer free radicals should result in less cellular damage and a longer life. However, antioxidants alone have not been shown to prolong longevity
Other studies performed on a wide variety of animals showed that calorie restriction enhances the immune response in older animals, thus reducing the onset of fatal age-related diseases. Paradoxically, it seems to impair this system in young animals, and this may be why calorie restriction in children is so dangerous, as in cases of anorexia or in famine-stricken areas of the world. Calorie-restricted monkeys also have decreased triglyceride levels and increased levels of HDL, the good cholesterol, thereby reducing the risk of dying from cardiovascular disease. Calorie restriction also increases insulin sensitivity, allowing the hormone to more effectively control blood sugar and delay adult-onset diabetes, which frequently causes premature death.
But the main action of calorie restriction was to prolong the healthy, disease-free period of life and postpone the period of rapid decline near the end of life. As an added bonus, these studies confirmed that calorie restriction positively affected health even if not started until middle age. It’s never too late to start!
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